Sunday, March 31, 2013

630m operation and Class E at Home Brew Group

Two excellent talks at the ARNSW Home Brew Group meeting today. The main talk was by Nick, VK2DX, who talked about getting on the 630 meter band (472-479kHz).

Nick talked about his long history of listening to interesting things he's seen on the waterfall including over the horizon radar and non directional beacons. Getting on air with such a low frequency is a challenge anywhere but particularly in a dense metropolitan area.

The challenge is the antenna and matching to it. Ironically, while the best antenna is something huge like a beverage antenna, the second best is a tiny E-Field probe like the PA0RDT mini whips.

Nick uses a vertical antenna that is resonant on 80m but with the addition of a huge 600uH loading coil (60 turns on a bucket), a home built variometer and an impudence matching transformer he's getting to QLD, SA and NZ using the WSPR mode.

The supporting talk was my regular Mike, VK2BMR who talked about his experiments making a tesla generator operating in class E.

Mike is getting great efficiency, which is the great benefit of Class E, and his biggest challenge seems to have been to build attenuators and dummy loads that can handle the power he's generating. I was hoping for a demonstration with a bit of indoor lightning but maybe next time.

As always, thanks to the organisers for another great day at Dural.

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